1. Field of the Invention
The present invention relates to a communication device that performs automatic failure recovery and an automatic failure recovery method and, more particularly, to a communication device and an automatic failure recovery method for realizing shortening of failure recovery time.
2. Description of the Related Art
Concomitant with the growth in communication demands, various layers exist in a communication network, including the Optical Transport Network (OTP) layer (see ITU-T Recommendation G.709 Ver.1), the SDH layer, the PDH layer, the IP layer, etc., which are contained in a hierarchical relationship.
For example, an IP packet is mapped to an SDH signal, and it is further mapped to an OTN frame.
In addition, in some cases, to address a failure in each layer, each layer has a failure recovery function.
For example, the OTN layer has a failure recovery function such as OCh SPRing (see ITU-T Recommendation Draft G.872 ver1.4 or later), and the SDH layer has a failure recovery function such as MS SPRing.
The IP layer has a function that bypasses an IP packet automatically through a routing protocol in the event of a communication failure.
Thus, in a system in which each layer has its own failure recovery function, if each layer is not aware of the other layers and is operated independently, in some cases, due to switching in each layer, a conflict is generated in the network topology recognized by each layer, and ultimately, failures cannot be recovered.
In the past, a configuration such as the one shown in FIG. 13 was conceived as a device configuration that solves the complexity of failure recovery in systems consisting of multiple layers (Japanese Unexamined Patent Publication (Kokai) No. 2000-278285).
In FIG. 13, reference numeral 1201 is a main network management system (Main-NMS), reference numerals 1202 through 1204 are sub network management systems, reference numeral 1227 is a manager, reference numeral 1228 is an agent, and reference numerals 1224 through 1226 are groups of path objects in mutually different layers corresponding to SDH_VC12-TU12, SDH_VC3-AU3, etc.
Further, in a bus failure recovery function 1220, reference numeral 1221 is a communication path failure reception unit, reference numeral 1222 is a communication path recovery target selection unit, and reference numeral 1223 is a communication path recovery processing unit.
All of the above is included in the main network management system 1201.
Then, if a failure occurs in the system and if the failure is detected by the communication path failure reception unit 1221, which layer and which auxiliary paths will be used for failure recovery is calculated and selected in the communication path recovery target selection unit 1222, by referring to failure information, path usage rate information, etc., on all layers, to perform failure recovery processing of the selected layer in the communication path recovery processing unit 1223.
With the configuration as described above, if the multiple layers had a failure recovery function, coordinated operation of failure recovery could be performed.
In a similar problem, as shown in FIG. 14, there are cases where, although there is only one path layer to handle, i.e. a path 1300, multiple failure recovery areas may exist therein.
In FIG. 14, reference numeral 1300 is the path, A and B are failure recovery areas, and reference numerals 1303 through 1306 are nodes.
Even when multiple failure recovery areas exist with respect to one path, as in the case of the failure recovery areas A and B, a conventional method that uses an NMS used for cases involved in multiple layers can be applied as a method that coordinates the multiple failure recovery areas in a network involved in multiple failure recovery areas.
As described above, the conventional communication system had such problems as the ones described below.
When involved in multiple layers, if the conventional method is used, since the main network management system (NMS) has to perform failure recovery processing by referring to failure information, path usage rate information, etc., on all layers, the load on NMS increases, the size of the NMS device increases, and the cost rises.
In addition, since one system, i.e. the NMS, performs everything from selection of a bypass layer to setting of auxiliary paths, the failure cannot be handled if a failure occurs in the NMS.
Further, it takes time to search for the most suitable layer such that as a whole, there is a delay in the failure recovery time.
When the conventional method that uses an NMS used for cases involved in multiple layers is applied as a method that coordinates multiple failure recovery areas in the network involved in multiple failure recovery areas with respect to one path, since the NMS has to perform failure recovery processing by referring to failure information, path usage rate information, etc., on all layers, the load on NMS increases, the size of the NMS device increases, and the cost rises.
In addition, as described above, since one system, i.e. the NMS, performs everything from selection of a bypass failure recovery area to setting of auxiliary paths, the failure cannot be handled if a failure occurs in the NMS. Further, also in this case, it takes time to search for the most suitable failure recover area such that as a whole, there is a delay in the failure recovery time.